Buggy code:
public class CustomersDataService { public static List < Customer > get ( String query , int limit , int offset ) { List < Customer > list = null ; String sql = null ; try ( Connection conn = sql2o . open ( ) ) { <START_BUG> if ( query . equals ( null ) ) { <END_BUG> sql = "select<seq2seq4repair_space>*<seq2seq4repair_space>from<seq2seq4repair_space>customer" ; list = conn . createQuery ( sql ) . executeAndFetch ( Customer . class ) ; } else { sql = "select<seq2seq4repair_space>*<seq2seq4repair_space>from<seq2seq4repair_space>customer<seq2seq4repair_space>where<seq2seq4repair_space>" ; while ( query != null ) { int equal_pos = query . indexOf ( '=' ) ; sql = ( sql + ( query . substring ( 0 , equal_pos ) ) ) + "<seq2seq4repair_space>=<seq2seq4repair_space>" ; int and_op = query . indexOf ( '&' ) ; int or_op = query . indexOf ( "||" ) ; System . out . println ( "and" ) ; if ( ( and_op >= 0 ) && ( or_op == ( - 1 ) ) ) { if ( CustomersDataService . isNumeric ( query . substring ( ( equal_pos + 1 ) , and_op ) ) ) { sql = ( sql + ( query . substring ( ( equal_pos + 1 ) , and_op ) ) ) + "<seq2seq4repair_space>and<seq2seq4repair_space>" ; } else { sql = ( ( ( sql + "'" ) + ( query . substring ( ( equal_pos + 1 ) , and_op ) ) ) + "'" ) + "<seq2seq4repair_space>and<seq2seq4repair_space>" ; } query = query . substring ( ( and_op + 1 ) ) ; } else if ( ( or_op >= 0 ) && ( and_op == ( - 1 ) ) ) { if ( CustomersDataService . isNumeric ( query . substring ( ( equal_pos + 1 ) , or_op ) ) ) { sql = ( sql + ( query . substring ( ( equal_pos + 1 ) , or_op ) ) ) + "<seq2seq4repair_space>or<seq2seq4repair_space>" ; } else { sql = ( ( ( sql + "'" ) + ( query . substring ( ( equal_pos + 1 ) , or_op ) ) ) + "'" ) + "<seq2seq4repair_space>or<seq2seq4repair_space>" ; } query = query . substring ( ( or_op + 2 ) ) ; } else if ( ( or_op >= 0 ) && ( and_op >= 0 ) ) { if ( and_op < or_op ) { if ( CustomersDataService . isNumeric ( query . substring ( ( equal_pos + 1 ) , and_op ) ) ) { sql = ( sql + ( query . substring ( ( equal_pos + 1 ) , and_op ) ) ) + "<seq2seq4repair_space>and<seq2seq4repair_space>" ; } else { sql = ( ( ( sql + "'" ) + ( query . substring ( ( equal_pos + 1 ) , and_op ) ) ) + "'" ) + "<seq2seq4repair_space>and<seq2seq4repair_space>" ; } query = query . substring ( ( and_op + 1 ) ) ; } else if ( or_op < and_op ) { if ( CustomersDataService . isNumeric ( query . substring ( ( equal_pos + 1 ) , or_op ) ) ) { sql = ( sql + ( query . substring ( ( equal_pos + 1 ) , or_op ) ) ) + "<seq2seq4repair_space>or<seq2seq4repair_space>" ; } else { sql = ( ( ( sql + "'" ) + ( query . substring ( ( equal_pos + 1 ) , or_op ) ) ) + "'" ) + "<seq2seq4repair_space>or<seq2seq4repair_space>" ; } query = query . substring ( ( or_op + 2 ) ) ; } } else { if ( CustomersDataService . isNumeric ( query . substring ( ( equal_pos + 1 ) ) ) ) { sql = sql + ( query . substring ( ( equal_pos + 1 ) ) ) ; } else { sql = ( ( sql + "'" ) + ( query . substring ( ( equal_pos + 1 ) ) ) ) + "'" ; } query = null ; } } list = conn . createQuery ( sql ) . executeAndFetch ( Customer . class ) ; } return list ; } } public static Customer get ( int customer_id ) { } public static void create ( Customer customer ) { } public static void delete ( int customer_id ) { } public static void update ( Customer customer ) { } public static boolean isNumeric ( String str ) { } }

Fix:
if ( query == null ) {